Neuron
a nerve cell; the basic building block of the nervous system
Dendrites
a neuron's bushy, branching extensions that receive messages and conduct impulses toward the cell body
Axon
the neuron extension that passes messages through its branches to other neurons or to muscles or glands
Myelin Sheath
a fatty tissue layer segmentally encasing the axons of some neurons; enables vastly greater transmission speed as neural impulses hop from one sausage-like node to the next
Action potential
a neural impulse; a brief electrical charge that travels down an axon
Refractory Period
a period of inactivity after a neuron fires
Threshold
the level of stimulation required to trigger a neural impulse
All-or-None Response
a neuron's reaction of either firing or not firing
Synapse
the junction between the axon tip of the sending neuron and the dendrite or cell body of the receiving neuron. The tiny gap at this junction is called the synaptic gap or synaptic cleft
Neurotransmitters
chemical messengers that cross the synaptic gaps between neurons. When released by the sending neuron, neurotransmitters travel across the synapse and bind to receptor sites on the receiving neuron, thereby influencing whether that neuron will generate a neural impulse
Reuptake
a neurotransmitter's reabsorption by the sending neuron
Endorphins
"morphine within" - natural, opiate-like neurotransmitters linked to pain control and to pleasure
Agonist
a molecule that, by binding to a receptor site, stimulates a response
Antagonist
a molecule that, by binding to a receptor site, inhibits or blocks a response
Nervous System
the body's speedy, electrochemical communication network, consisting of all the nerve cells of the peripheral and central nervous systems
Central Nervous System
the brain and spinal cord
Peripheral Nervous System
the sensory and motor neurons that connect the central nervous system to the rest of the body
Nerves
bundled axons that form neural "cables" connecting the central nervous system with muscles, glands, and sense organs
Sensory (afferent) neurons
neurons that carry incoming information from the sensory receptors to the brain and spinal cord
Motor (efferent) neurons
neurons that carry outgoing information from the brain and spinal cord to the muscles and glands
Interneurons
neurons within the brain and spinal cord that communicate internally and intervene between the sensory inputs and motor outputs
Somatic Nervous System
the division of the periperal nervous system that controls the body's skeletal muscles.
Autonomic Nervous System
the part of the peripheral nervous system that controls the glands and the muscles of the internal organs. Its sympathetic division arouses, its parasympathetic division calms
Sympathetic Nervous System
the division of the autonomic nervous system that arouses the body, mobilizing its energy in stressful situations
Parasympathetic Nervous Systems
the division of the autonomic nervous system that calms the body, conserving its energy
Reflex
a simple, automatic response to a sensory stimulus, such as the knee-jerk response
Endocrine System
the body's "slow" chemical communication system; a set of glands that secrete hormones into the bloodstream
Hormones
chemical messengers that are manufactured by the endocrine glands travel through the bloodstream and affect other tissues
Adrenal Glands
a pair of endocrine glands that sit just above the kidneys and secrete hormones that help arouse the body in times of stress
Pituitary Gland
the endocrine system's most influential gland. Under the influence of the hypothalamus, the pituitary regulates growth and controls other endocrine glands
Glia Cells
cells in the nervous system that support, nourish, and protect neurons
Schwann cells
Supporting cells of the peripheral nervous system responsible for the formation of myelin.
Polarization
cell at it's resting potential. negative inside, positive outside
Depolarization
The process during the action potential when sodium is rushing into the cell causing the interior to become more positive.
excitory neurotransmitters
neurotransmitters that promote action potential, causing depolarization. Some neurotransmitters are excitatory, some are inhibitory, but most can be either.
inhibitory neurotransmitters
neurotransmitters that inhibit the next cell from firing
Acetylcholine
A neurotransmitter that enables learning and memory and also triggers muscle contraction. Too little leads to alzheimers
Epinephrine
Neurotransmitter secreted by the adrenal medulla in response to stress. Also known as adrenaline.
Norepinephrine
A neurotransmitter involved in arousal, as well as in learning and mood regulation
Glutamate
A major excitatory neurotransmitter; involved in memory
GABBA
inhibitory neurotransmitter that calms you down
Dopamine
influences movement, learning, attention, and emotion. Too much leads to schiznophrenia. Too little leads to parkinsons
Serotonin
Affects mood, hunger, sleep, and arousal
Endorphins
"morphine within"--natural, opiatelike neurotransmitters linked to pain control and to pleasure.
axon terminals (terminal buttons)
Enlarged button like structures at the ends of axon branches that release neurotransmitters